Dressing And Method For Applying Reduced Pressure To And Collecting And Storing Fluid From A Tissue Site

ABSTRACT

A reduced pressure dressing for applying reduced pressure treatment to a tissue site includes an interface layer adapted to be positioned at the tissue site. An absorbent layer is in fluid communication with the interface layer to absorb liquid from at least one of the interface layer and the tissue site. A pump is in fluid communication with the absorbent layer to deliver a reduced pressure to the tissue site. A cover is positioned over the pump, the absorbent layer, and the interface layer to maintain the reduced pressure at the tissue site, and a liquid-air separator is positioned between the absorbent layer and the pump to inhibit liquid from entering the pump.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/944,639, filed Apr. 3, 2018, which is a continuation of U.S.application Ser. No. 14/703,667, filed May 4, 2015 which is a divisionalof U.S. application Ser. No. 13/709,255, filed Dec. 10, 2012, now U.S.Pat. No. 9,050,209, which is a continuation of U.S. application Ser. No.12/398,904, filed Mar. 5, 2009, now U.S. Pat. No. 8,372,050, whichclaims the benefit of U.S. Provisional Application No. 61/034,013, filedMar. 5, 2008, and U.S. Provisional Application No. 61/049,028, filedApr. 30, 2008. Each of the applications referenced above are herebyincorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to tissue treatment systems andin particular to dressings for distributing reduced pressure to andcollecting and storing fluid from a tissue site.

2. Description of Related Art

Clinical studies and practice have shown that providing a reducedpressure in proximity to a tissue site augments and accelerates thegrowth of new tissue at the tissue site. The applications of thisphenomenon are numerous, but application of reduced pressure has beenparticularly successful in treating wounds. This treatment (frequentlyreferred to in the medical community as “negative pressure woundtherapy,” “reduced pressure therapy,” or “vacuum therapy”) provides anumber of benefits, including faster healing and increased formulationof granulation tissue. Typically, reduced pressure is applied to tissuethrough a porous pad or other manifold device. The porous pad containscells or pores that are capable of distributing reduced pressure to thetissue and channeling fluids that are drawn from the tissue. The porouspad may be incorporated into a dressing having other components thatfacilitate treatment.

SUMMARY

The problems presented by existing collection canisters are solved bythe systems and methods of the illustrative embodiments describedherein. In one illustrative embodiment, a reduced pressure dressing forapplying reduced pressure treatment to a tissue site is provided. Thereduced pressure dressing includes an interface layer adapted to bepositioned at the tissue site. An absorbent layer is in fluidcommunication with the interface layer to absorb liquid from at leastone of the interface layer and the tissue site. A pump is in fluidcommunication with the absorbent layer to deliver a reduced pressure tothe tissue site. A cover is positioned over the pump, the absorbentlayer, and the interface layer to maintain the reduced pressure at thetissue site, and a liquid-air separator is positioned between theabsorbent layer and the pump to inhibit liquid from entering the pump.

In another illustrative embodiment, a reduced pressure dressing forapplying reduced pressure treatment to a tissue site includes aninterface layer adapted to be positioned at the tissue site. Anabsorbent layer is in fluid communication with the interface layer toabsorb liquid from at least one of the interface layer and the tissuesite. A pump is in fluid communication with the absorbent layer todeliver a reduced pressure to the tissue site. A diverter layer ispositioned between the absorbent layer and the pump, and the diverterlayer includes a plurality of apertures to transmit the reduced pressurefrom the pump to the absorbent layer. A cover is positioned over thepump, the diverter layer, the absorbent layer, and the interface layerto maintain the reduced pressure at the tissue site. A liquid-airseparator is positioned between the diverter layer and the pump toinhibit liquid from entering the pump.

In another illustrative embodiment, a reduced pressure dressing forapplying reduced pressure treatment to a tissue site is provided. Thereduced pressure dressing includes an interface layer adapted to bepositioned at the tissue site and an absorbent layer in fluidcommunication with the interface layer to absorb liquid from at leastone of the interface layer and the tissue site. A diverter layer isadjacent the absorbent layer, and the diverter layer is formed from asubstantially gas-impermeable material. The diverter layer includes aplurality of apertures in fluid communication with the absorbent layerto increase an amount of time that the absorbent layer is able todistribute reduced pressure. A pump is in fluid communication with theplurality of apertures of the diverter layer to deliver a reducedpressure to the tissue site. A cover is positioned over the pump, thediverter layer, the absorbent layer, and the interface layer to maintainthe reduced pressure at the tissue site. A liquid-air separator ispositioned between the diverter layer and the pump to inhibit liquidfrom entering the pump.

In still another illustrative embodiment, a reduced pressure dressingfor applying reduced pressure treatment to a tissue site is provided.The reduced pressure dressing includes an interface layer adapted to bepositioned at the tissue site. A first manifold layer is in fluidcommunication with the interface layer, and an absorbent layer is influid communication with the first manifold layer to absorb liquid fromat least one of the first manifold layer, the interface layer, and thetissue site. A diverter layer is formed from a substantiallygas-impermeable material, and the diverter layer includes a plurality ofspaced apertures in fluid communication with the absorbent layer. Asecond manifold layer is in fluid communication with the diverter layer.A pump is in fluid communication with the second manifold layer todeliver a reduced pressure to the tissue site. A cover is positionedover the pump, the second manifold layer, the diverter layer, theabsorbent layer, the first manifold layer, and the interface layer tomaintain the reduced pressure at the tissue site. A liquid-air separatoris positioned between the second manifold and the pump to inhibit liquidfrom entering the pump.

In yet another illustrative embodiment, a method for collecting liquidin a dressing positioned at a tissue site includes generating a reducedpressure using a pump positioned within the dressing. A liquid isabsorbed from the tissue site and is stored in the dressing. The liquidis prevented from entering the pump.

In another illustrative embodiment, a reduced pressure dressing adaptedto distribute a reduced pressure to a tissue site includes an interfacelayer adapted to be positioned at the tissue site. An absorbent layer isin fluid communication with the interface layer to absorb liquid from atleast one of the interface layer and the tissue site. A pump is in fluidcommunication with the absorbent layer to deliver the reduced pressureto the tissue site, a diverter layer is positioned between the absorbentlayer and the pump. The diverter layer is formed from a substantiallygas-impermeable material and includes a surface area smaller than asurface area of the absorbent layer such that flow is directed around atleast one perimeter edge of the diverter layer. A cover is positionedover the diverter layer to maintain the reduced pressure at the tissuesite.

In still another illustrative embodiment, a reduced pressure dressingadapted to distribute a reduced pressure to a tissue site is provided.The dressing includes an interface layer adapted to be positioned at thetissue site. An absorbent layer is in fluid communication with theinterface layer to absorb liquid from at least one of the interfacelayer and the tissue site. A pump is in fluid communication with theabsorbent layer to deliver the reduced pressure to the tissue site, anda diverter layer is positioned between the absorbent layer and the pump.The diverter layer is formed from a substantially gas-permeable, liquidimpermeable material. A cover is positioned over the diverter layer tomaintain the reduced pressure at the tissue site.

Other objects, features, and advantages of the illustrative embodimentswill become apparent with reference to the drawings and detaileddescription that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a reduced pressure treatmentsystem according to an illustrative embodiment, the reduced pressuretreatment system having a dressing positioned at a tissue site;

FIG. 2 depicts a cross-sectional front view of the dressing of FIG. 1taken at 2-2;

FIG. 3 illustrates an exploded perspective view of the dressing of FIG.1;

FIG. 4 depicts a top view of a diverter layer the dressing of FIG. 3;

FIG. 5 illustrates a top view of a diverter layer according to anillustrative embodiment;

FIG. 6 depicts a top view of the diverter layer of FIG. 5;

FIG. 7 illustrates a perspective view of a diverter layer according toan illustrative embodiment;

FIG. 8 depicts a top view of the diverter layer of FIG. 7;

FIG. 9 illustrates a top view of a diverter layer according to anillustrative embodiment;

FIG. 10 depicts an exploded perspective view of a reduced pressuredressing according to an illustrative embodiment;

FIG. 11 illustrates a top view of a drape for use with a reducedpressure dressing according to an illustrative embodiment;

FIG. 12 depicts a cross-sectional front view of the drape of FIG. 11;

FIG. 13 illustrates a cross-sectional front view of a drape for use witha reduced pressure dressing according to an illustrative embodiment;

FIG. 14 depicts a top view of a tissue interface layer for use with areduced pressure dressing according to an illustrative embodiment;

FIG. 15 illustrates a top view of a tissue interface layer for use witha reduced pressure dressing according to an illustrative embodiment;

FIG. 16 depicts a graph showing vacuum pressure versus time for areduced pressure treatment system applying reduced pressure to a tissuesite according to an illustrative embodiment;

FIG. 17 illustrates an exploded perspective view of a reduced pressuretreatment dressing according to an illustrative embodiment;

FIG. 18 depicts a perspective view of a reduced pressure treatmentsystem according to an illustrative embodiment, the reduced pressuretreatment system having a dressing with an integrated pump positioned ata tissue site;

FIG. 19 illustrates a cross-sectional front view of the dressing andpump of FIG. 18 taken at 19-19; and

FIG. 20 depicts an exploded perspective view of the dressing and pump ofFIG. 18.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the following detailed description of several illustrativeembodiments, reference is made to the accompanying drawings that form apart hereof, and in which is shown by way of illustration specificpreferred embodiments in which the invention may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the invention, and it is understood that otherembodiments may be utilized and that logical structural, mechanical,electrical, and chemical changes may be made without departing from thespirit or scope of the invention. To avoid detail not necessary toenable those skilled in the art to practice the embodiments describedherein, the description may omit certain information known to thoseskilled in the art. The following detailed description is, therefore,not to be taken in a limiting sense, and the scope of the illustrativeembodiments are defined only by the appended claims.

The term “reduced pressure” as used herein generally refers to apressure less than the ambient pressure at a tissue site that is beingsubjected to treatment. In most cases, this reduced pressure will beless than the atmospheric pressure at which the patient is located.Alternatively, the reduced pressure may be less than a hydrostaticpressure associated with tissue at the tissue site. Although the terms“vacuum” and “negative pressure” may be used to describe the pressureapplied to the tissue site, the actual pressure reduction applied to thetissue site may be significantly less than the pressure reductionnormally associated with a complete vacuum. Reduced pressure mayinitially generate fluid flow in the area of the tissue site. As thehydrostatic pressure around the tissue site approaches the desiredreduced pressure, the flow may subside, and the reduced pressure is thenmaintained. Unless otherwise indicated, values of pressure stated hereinare gauge pressures. Similarly, references to increases in reducedpressure typically refer to a decrease in absolute pressure, whiledecreases in reduced pressure typically refer to an increase in absolutepressure.

The term “tissue site” as used herein refers to a wound or defectlocated on or within any tissue, including but not limited to, bonetissue, adipose tissue, muscle tissue, neural tissue, dermal tissue,vascular tissue, connective tissue, cartilage, tendons, or ligaments.The term “tissue site” may further refer to areas of any tissue that arenot necessarily wounded or defective, but are instead areas in which itis desired to add or promote the growth of additional tissue. Forexample, reduced pressure tissue treatment may be used in certain tissueareas to grow additional tissue that may be harvested and transplantedto another tissue location.

Reduced pressure treatment systems are often applied to large, highlyexudating wounds present on patients undergoing acute or chronic care,as well as other severe wounds that are not readily susceptible tohealing without application of reduced pressure. Low-severity woundsthat are smaller in volume and produce less exudate have generally beentreated using advanced dressings instead of reduced pressure treatment.These advanced dressings, however, are not adapted for use with reducedpressure and are subject to several drawbacks when used in conjunctionwith reduced pressure. For example, these current dressings may fail tomake optimal use of fluid storage capacity in the dressing.Additionally, existing dressings are not configured to adequatelytransmit reduced pressure, especially as the dressings begin to absorband store fluid.

Currently, the use of reduced pressure treatment is not considered aviable or affordable option for low-severity wounds due to the manpowerrequired to monitor and change system components, the requirement fortrained medical personnel overseeing treatment, and the cost oftreatment. For example, the complexity of current reduced pressuretreatment systems limits the ability of a person with little or nospecialized knowledge from administering such treatment to oneself orothers. The size of current reduced pressure treatment systems alsoimpairs the mobility of both the treatment system and the person to whomthe treatment is being applied. For example, current reduced pressuretreatment systems require the use of a separate canister that storesexudate or other liquid from the tissue site. Current reduced pressuretreatment systems are also typically non-disposable after eachtreatment, and require electrical components or other powered devices inorder to apply the reduced pressure used in treatment.

Reduced Pressure Dressing

Referring to FIG. 1, a reduced pressure treatment system 100 accordingto an illustrative embodiment includes a reduced pressure dressing 104positioned at a tissue site 108 of a patient. The reduced pressuredressing 104 is fluidly connected to a reduced pressure source 110 by aconduit 112. The conduit 112 may fluidly communicate with the reducedpressure dressing 104 through a tubing adapter 116. In the embodimentillustrated in FIG. 1, the reduced pressure source 110 is amanually-actuated pump such as, for example, a compressible bellowspump. In another implementation, the reduced pressure source 110 may bea reduced pressure or vacuum pump driven by a motor. In anotherembodiment, the reduced pressure source 110 may be a powered micropumpsuch as, for example, a piezoelectric disc pump, or alternatively aperistaltic pump. In still another embodiment, the reduced pressuresource 110 may be a wall suction port such as are available in hospitalsand other medical facilities.

The reduced pressure source 110 may be housed within a reduced pressuretreatment unit, which may also contain sensors, processing units, alarmindicators, memory, databases, software, display units, and userinterfaces that further facilitate the application of reduced pressuretreatment to the tissue site 108. In one example, a sensor or switch(not shown) may be disposed at or near the reduced pressure source 110to determine a source pressure generated by the reduced pressure source110. The sensor may communicate with a processing unit that monitors andcontrols the reduced pressure that is delivered by the reduced pressuresource 110. Delivery of reduced pressure to the reduced pressuredressing 104 and tissue site 108 encourages new tissue growth bymaintaining drainage of exudate from the tissue site, increasing bloodflow to tissues surrounding the tissue site, and creating microstrain atthe tissue site.

Referring to FIGS. 2 and 3, the reduced pressure dressing 104 includesan interface layer 220 adapted to be positioned at the tissue site 108,and a seal layer 222 to seal the reduced pressure dressing 104 aroundthe tissue site 108. A first manifold layer 224 is in fluidcommunication with the interface layer 220 to distribute the reducedpressure to the interface layer 220 and the tissue site 108. Anabsorbent layer 228 is positioned in fluid communication with the firstmanifold layer 224 to absorb liquid from at least one of the firstmanifold layer 224, the interface layer 220, and the tissue site 108. Adiverter layer 232 is positioned adjacent the absorbent layer 228. Asecond manifold layer 236 is positioned in fluid communication with thediverter layer 232, and a liquid-air separator 240 is positionedadjacent the second manifold layer 236. A cover 244, or drape, ispositioned adjacent the liquid-air separator 240.

The interface layer 220 of the reduced pressure dressing 104 is adaptedto contact the tissue site 108. The interface layer 220 may be partiallyor fully in contact with the tissue site 108 being treated by thereduced pressure dressing 104. When the tissue site 108 is a wound, theinterface layer 220 may partially or fully fill the wound.

The interface layer 220 may be any size, shape, or thickness dependingon a variety of factors, such as the type of treatment being implementedor the nature and size of the tissue site 108. For example, the size andshape of the interface layer 220 may be customized by a user to cover aparticular portion of the tissue site 108, or to fill or partially fillthe tissue site 108. Although the interface layer 220 illustrated inFIG. 3 has a square shape, the interface layer 220 may be shaped as acircle, oval, polygon, an irregular shape, or any other shape.

In one illustrative embodiment, the interface layer 220 is a foammaterial that functions as a manifold to provide reduced pressure to thetissue site 108 when the interface layer 220 is in contact with or nearthe tissue site 108. The foam material may be either hydrophobic orhydrophilic. In one non-limiting example, the interface layer 220 is anopen-cell, reticulated polyurethane foam such as GranuFoam® dressingavailable from Kinetic Concepts, Inc. of San Antonio, Tex.

In the example in which the interface layer 220 is made from ahydrophilic material, the interface layer 220 also functions to wickfluid away from the tissue site 108, while continuing to provide reducedpressure to the tissue site 108 as a manifold. The wicking properties ofthe interface layer 220 draw fluid away from the tissue site 108 bycapillary flow or other wicking mechanisms. An example of a hydrophilicfoam is a polyvinyl alcohol, open-cell foam such as V.A.C. WhiteFoam®dressing available from Kinetic Concepts, Inc. of San Antonio, Tex.Other hydrophilic foams may include those made from polyether. Otherfoams that may exhibit hydrophilic characteristics include hydrophobicfoams that have been treated or coated to provide hydrophilicity.

The interface layer 220 may further promote granulation at the tissuesite 108 when a reduced pressure is applied through the reduced pressuredressing 104. For example, any or all of the surfaces of the interfacelayer 220 may have an uneven, coarse, or jagged profile that causesmicrostrains and stresses at the tissue site 108 when reduced pressureis applied through the interface layer 220. These microstrains andstresses have been shown to increase new tissue growth.

In one embodiment, the interface layer 220 may be constructed frombioresorbable materials that do not have to be removed from a patient'sbody following use of the reduced pressure dressing 104. Suitablebioresorbable materials may include, without limitation, a polymericblend of polylactic acid (PLA) and polyglycolic acid (PGA). Thepolymeric blend may also include without limitation polycarbonates,polyfumarates, and capralactones. The interface layer 220 may furtherserve as a scaffold for new cell-growth, or a scaffold material may beused in conjunction with the interface layer 220 to promote cell-growth.A scaffold is a substance or structure used to enhance or promote thegrowth of cells or formation of tissue, such as a three-dimensionalporous structure that provides a template for cell growth. Illustrativeexamples of scaffold materials include calcium phosphate, collagen,PLA/PGA, coral hydroxy apatites, carbonates, or processed allograftmaterials.

The seal layer 222 of the reduced pressure dressing 104 includes anaperture or opening 231 and provides a seal around the tissue site 108.The seal layer 222 may serve as a gasket around a portion of the tissuesite 108 to prevent reduced pressure applied to the reduced pressuredressing 104 from leaking out of the reduced pressure dressing 104. Theseal layer 222 may also be used to secure the interface layer 220 at thetissue site 108. If the cover 244 is applied to the tissue surroundingthe tissue site 108 with wrinkles in the cover 244, then the seal layer222 assists in maintaining in the wrinkled areas of the cover 244.

The seal layer 222 may be any size and thickness capable of providing aseal around the tissue site 108. In the example of FIG. 2, a length, L2,and a width, W2, of the seal layer 222 are greater than a length, LI,and a width, W1, of the interface layer 220, respectively. Thus,portions of the seal layer 222 extend past the edges of the interfacelayer 220. These portions may contact the tissue surrounding the tissuesite 108 directly, thereby providing a seal around the tissue site 108and the interface layer 220.

While the seal layer 222 illustrated in FIG. 3 has a square shape, theseal layer 222 may also have any other shape that provides a seal aroundthe tissue site 108 or the interface layer 220. Non-limiting examples ofother shapes include a circle, oval, any polygonal shape, an irregularshape, or a shape that is customized to contour to the tissuesurrounding the tissue site 108 or the interface layer 220.

The seal layer 222 may be made from any material that is capable ofsealing around the treated portion of the tissue site 108. In oneillustrative embodiment, the seal layer 222 may include or be made froma hydrogel. The seal layer 222 may also include either or both of ahydrocolloid or silicon.

Although the seal layer 222 is shown as being disposed adjacent to theinterface layer 220, the seal layer 222 may be positioned adjacent orbetween any of the layers in the reduced pressure dressing 104.Additional details regarding the positioning of the seal layer 222 arediscussed in more detail below with reference to FIG. 2.

The reduced pressure dressing 104 also includes a first manifold layer224 for distributing the reduced pressure to and withdrawing liquid,such as exudate, from the interface layer 220. When the seal layer 222is positioned adjacent the interface layer 220, liquid may be withdrawnfrom the tissue site 108 through the aperture 231. As a reduced pressureis applied to the reduced pressure dressing 104, the liquid is wickedfrom the tissue site 108 by the interface layer 220 and drawn throughthe aperture 231 of the seal layer 222 by the first manifold layer 224.

In one embodiment, a length, L3, and a width, W3, of the aperture 231 isless than the length, L1, and the width, W1, of the interface layer 220.However, in other embodiments, particularly in those embodiments inwhich one or more other layers are disposed between the seal layer 222and the interface layer 220, the length, L3, and the width, W3, of theaperture 231 may be equal to or larger than the length, L1, and thewidth, W1, of the interface layer 220. While the aperture 231illustrated in FIG. 3 has a square shape, the aperture 231 may insteadhave any other shape that allows the seal layer 222 to provide a sealwhile facilitating the passage of liquid from the tissue site 108.

The first manifold layer 224 may have any size, shape, or thickness. Forexample, the size and shape of the first manifold layer 224 may becustomized to provide differing levels of utilization of the absorbentlayer 228. The size and shape of the first manifold layer 224 may alsobe customized based on the size and shape of other components in thereduced pressure dressing 104, such as the size and shape of theinterface layer 220, the seal layer 222, the aperture 231, the absorbentlayer 228, or other layers in the reduced pressure dressing 104.

The first manifold layer 224 is a biocompatible, porous material that iscapable of distributing reduced pressure to the tissue site 108. Thefirst manifold layer 224 may be made from foam, gauze, felted mat, orany other material suited to a particular biological application. Thefirst manifold layer 224 includes a plurality of flow channels orpathways to facilitate distribution of reduced pressure or fluids to orfrom the tissue site 108. In one embodiment, the first manifold layer224 is a porous foam and includes a plurality of interconnected cells orpores that act as flow channels. The porous foam may be a polyurethane,open-cell, reticulated foam such as GranuFoam® dressing. If an open-cellfoam is used, the porosity may be about 400 to 600 microns or any otherporosity capable of adequately manifolding reduced pressure. The flowchannels allow fluid communication throughout the portion of firstmanifold layer 224 having open cells. The cells and flow channels may beuniform in shape and size, or may include patterned or random variationsin shape and size. Variations in the shape and size of the cells of thefirst manifold layer 224 result in variations in the flow channels, andsuch characteristics may be used to alter the flow characteristics offluid through first manifold layer 224. The first manifold layer 224 maybe either hydrophobic or hydrophilic. In one embodiment, the firstmanifold layer 224 may be made from the same material as the interfacelayer 220.

In one embodiment, the first manifold layer 224 may be made from amaterial that expands upon contact with a liquid, such as exudate fromthe tissue site 108, such that the first manifold layer 224 will fill awound site or otherwise contact the tissue site 108. In this embodiment,the first manifold layer 224 may enable the interface layer 220 to beremoved, thereby simplifying the construction and reducing the thicknessor profile of the reduced pressure dressing 104.

The absorbent layer 228 of the reduced pressure dressing 104 is disposedadjacent the first manifold layer 224 for receiving and absorbing theliquids distributed by the first manifold layer 224. The first manifoldlayer 224 facilitates the migration of liquid from the tissue site 108radially outward toward the edges of the first manifold layer 224, asindicated generally by the multi-directional arrows 239 so that theliquid is distributed more uniformly across the absorbent layer 228. Theabsorbent layer 228 will retain more liquid if the liquid is moreuniformly distributed across the surface of the absorbent layer 228.

As used herein, a “surface area” of a layer refers to an areameasurement of the layer as may be determined in a plane that ispositioned adjacent to or in contact with other layers. In the exampleillustrated in FIG. 3, the surface areas of the first manifold layer 224and the absorbent layer 228 are determined by multiplying the lengthsand widths of the respective layers, the lengths and widths beingmeasured in a plane substantially parallel to the plane containing thelength, L3, and the width, W3, of the aperture 231.

A surface area (defined as L3×W3) of the aperture 231 in FIG. 3 may beless than a surface area of the first manifold layer 224 and a surfacearea of the absorbent layer 228. If the first manifold layer 224 failedto distribute the liquid radially toward the edges of the first manifoldlayer 224, then the absorbent layer 228 would primarily absorb liquid ina portion of the absorbent layer 228 having a same size as the aperture231. However, because the first manifold layer 224 is capable ofradially distributing liquid from the tissue site 108 in the directionsindicated by the multi-directional arrows 239, a larger surface area ofthe absorbent layer 228 is exposed to the liquid, and the absorbentlayer 228 can store a larger volume of fluid. While the reduced pressuredressing 104 is designed primarily for use with reduced pressure, thedistribution of liquid from the tissue site 108 in the directionsindicated by the multi-directional arrows 239 may occur during theapplication of or in the absence of reduced pressure. A more completeutilization of the absorbent layer 228 may be achieved using the firstmanifold layer 224 even when reduced pressure is not being applied tothe reduced pressure dressing 104.

The absorbent layer 228 is adapted to absorb liquid, such as exudate,from the tissue site 108 via the interface layer 220 and the firstmanifold layer 224 through the aperture 231 of the seal layer 222. Theabsorbent layer 228 is also adapted to manifold and transfer reducedpressure through those layers to the tissue site 108. The absorbentlayer 228 may be made from any material capable of absorbing liquid,such as exudate from the tissue site 108. In one embodiment, theabsorbent layer 228 may be made from a super absorbent fiber. The superabsorbent fibers may hold onto or bond to the liquid in conjunction witha physical or chemical change to the fibers. In one non-limitingexample, the super absorbent fiber may include the Super Absorbent Fiber(SAF) material from Technical Absorbents®, Ltd. The absorbent layer 228may be a sheet or mat of fibrous material in which the fibers absorbliquid from the tissue site 108. The structure of the absorbent layer228 that contains the fibers may be either woven or non-woven. Thefibers in the absorbent layer 228 may gel upon contact with the liquid,thereby trapping the liquid. Spaces or voids between the fibers mayallow a reduced pressure that is applied to the reduced pressuredressing 104 to be transferred within and through the absorbent layer228. In one embodiment, the fiber density of fibers in the absorbentlayer 228 may be approximately 1.4 grams per millimeter.

The absorbent layer 228 may have any size, shape, or thickness. Ifadditional liquid storage capacity is desired for the reduced pressuredressing 104, then a larger or thicker absorbent layer 228 may be used.In another example, the size and thickness of the absorbent layer 228may be reduced for space-saving, convenience, compactness, or costconsiderations.

The reduced pressure dressing 104 may also include a diverter layer 232disposed adjacent to the absorbent layer 228, a second manifold layer236 disposed adjacent the diverter layer 232, and a liquid-air separator240 disposed adjacent the second manifold layer 236. The diverter layer232 includes a plurality of holes 247 though which reduced pressure fromthe reduced pressure source 110 (see FIG. 1) is applied. The reducedpressure is distributed to the diverter layer 232 by the second manifoldlayer 236. The holes 247 may be arranged in a pattern for applying thereduced pressure to portions of the absorbent layer 228 to enhance thecapability of the absorbent layer 228 to continue transferring thereduced pressure to the tissue site 108 as it absorbs more fluid fromthe tissue site 108. In the embodiment illustrated in FIG. 3, theplurality of holes 247 are positioned in a pattern around a peripheralportion of the diverter layer 232 away from the center of the diverterlayer 232 such that the reduced pressure is applied to the absorbentlayer 228 away from a center region of the absorbent layer 228. Thediverter layer 232 acts in conjunction with the first manifold layer 224to ensure that the absorption capabilities and absorption efficiency ofthe absorbent layer 228 is increased relative to an absorbent layer thatis not used in conjunction with a diverter layer. By providing betterdistribution of liquid throughout the absorbent layer 228, the diverterlayer 232 also increases an amount of time over which the absorbentlayer 228 is capable of manifolding reduced pressure in the dressing104.

The diverter layer 232 may be made from any material that enhances thereduced pressure transmission and storage capabilities of an adjacentabsorbent layer. For example, the diverter layer 247 may be made from amaterial that is substantially impermeable to liquid and gas.Alternatively, the material from which the diverter layer 232 is mademay instead have a predetermined moisture vapor transfer rate that isconsistent with gas permeability. In either example, the diverter layer232 may still include a pattern of holes for transmitting a greatervolume of liquid or gas than that permitted by the gas-permeablematerial of which the diverter layer 232 is constructed. It should benoted, however, that permeability of the diverter layer 232 to gas butnot liquid may result in increased transmission of reduced pressurethrough the dressing while still directing liquid flow around or nearthe perimeter of the diverter layer 232.

In the embodiment illustrated in FIG. 3, the reduced pressure createsfluid flow through the holes 247. The fluid flow through holes 247directs liquid pulled into the absorbent layer 228 away from a centerregion of the absorbent layer 228. The presence of holes 247 and thefluid flow through the holes 247 may also lessen the absorption rate ofliquid in the center region of the absorbent layer 228 and allow theabsorbent layer 228 to absorb liquid over a larger area. Thus, the gasand liquid are not limited only to traveling through the center of theabsorbent layer 228 or other layers that may be disposed closer to thetissue site 108 than the diverter layer 232. Because both the gas andliquid are directed radially outward toward the edges of the absorbentlayer 228, a greater portion of absorbent material is exposed to theliquid from the tissue site 108, and a larger portion of the absorbentlayer 228 may therefore be used to store or trap a greater volume of theliquid.

The fuller utilization of the absorbent layer 228 allows for the reducedpressure dressing 104 to be used for a longer period of time withouthaving to dispose the reduced pressure dressing 104. The need todistribute gas and liquid toward the edges of the absorbent layer 228may be even greater in the presence of reduced pressure due to the speedat which liquid may flow away from the tissue site 108 through thereduced pressure dressing 104.

The diverter layer 232 has primarily been described as assisting indiverting reduced pressure or fluid flow to a perimeter region of theabsorbent layer 228. Alternatively, the diverter layer 232 could insteadbe configured to assist in diverting reduced pressure to any particularregion, i.e. a target region, of the absorbent layer 228 to encourageliquid absorption within the target region. For example, if a tissuesite and a dressing were of a configuration that naturally resulted inliquid collection in a perimeter region of a particular absorbent layer,then a diverter layer could be configured to encourage liquid collectionwithin the center region of the absorbent layer. In this particularexample, the center region would be the target region.

Referring still to FIGS. 2 and 3, the second manifold layer 236distributes the reduced pressure more uniformly across the surface ofthe diverter layer 232. The second manifold layer 236 may be made fromany material capable of distributing or manifolding fluid. In oneexample, the second manifold layer 236 may be made from a same orsimilar material as the first manifold layer 224. In this example, thesecond manifold layer 236 may include a plurality of interconnectedcells that form a porous foam. The second manifold layer 236 may alsocollect liquid, such as exudate, from the tissue site 108 that is notabsorbed by the absorbent layer 228. The second manifold layer 236 mayhave any size, shape, or thickness.

In one embodiment of the reduced pressure dressing 104, the liquid-airseparator 240 may be a hydrophobic filter that inhibits or preventspassage of liquids through the liquid-air separator 240. Alternatively,the liquid-air separator 240 may be a gravity-based barrier system, or adevice that includes a hydrophilic surface to encourage condensation orother separation of liquid from a fluid stream when the fluid streampasses over the surface. Other examples of liquid-air separators 240 mayinclude sintered metals, sintered nylons, or any other material ordevice that is capable of separating liquid from a fluid stream, or thatis otherwise capable of inhibiting or preventing the passage of liquidwhile allowing the passage of gases.

By restraining or preventing the flow of liquid, the liquid-airseparator 240 prevents liquid from reaching the tubing adapter 116 orconduit 112 (see FIG. 1). By preventing liquid from reaching the conduit112, the liquid-air separator 240 also prevents the liquid from reachingthe reduced pressure source 110.

The liquid-air separator 240 may prevent the passage of reduced pressureto the tissue site 108 when the liquid-air separator 240 becomessaturated, clogged, blocked, and/or wetted with liquid from the tissuesite 108. The liquid-air separator 240 may also prevent the passage ofreduced pressure to the tissue site 108 when a layer that abuts theliquid-air separator 240 becomes saturated with liquid. For example, ifthe absorbent layer 228 abutted the liquid-air separator 240 in aparticular embodiment, the saturation of the absorbent layer 228 withliquid may cause the liquid-air separator 240 to prevent the passage ofreduced pressure. The presence of the diverter layer 232 between theliquid-air separator 240 and the absorbent layer 228 prolongs the periodof time before the liquid-air separator 240 blocks the passage ofreduced pressure.

The liquid-air separator 240 may have any size, shape, or thickness. Inone example, the liquid-air separator 240 may be smaller than otherlayers in the reduced pressure dressing 104 due to cost considerations.The liquid-air separator 240 may also be wider than the tubing adapter116 and an aperture 260 in the cover 244 so that liquid from the tissuesite 108 cannot reach the tubing adapter 116 or the aperture 260.

The cover 244 of the reduced pressure dressing 104 covers at least aportion of the reduced pressure dressing 104. In one embodiment, thecover 244 may fully cover the multiple layers of the reduced pressuredressing 104. In this embodiment, the cover 244 may secure or assist insecuring the reduced pressure dressing 104 to the tissue site 108 and inmaintaining a seal around the tissue site 108. In this respect, both thecover 244 and the seal layer 222 may work together to create a sealaround the tissue site 108. The cover 244 may also provide a protectivebarrier for the reduced pressure dressing 104 and the tissue site 108.

In the embodiment illustrated in FIGS. 2 and 3, the cover 244 may coverand secure components and layers between the cover 244 and the diverterlayer 232. In this embodiment, the cover 244 may be secured eitheradhesively or otherwise to the diverter layer 232. The diverter layer232, which may be made from a similar material as the cover 244, is thensecured to either or both of the seal layer 222 and the tissue at ornear the tissue site 108. The diverter layer 232 in this embodimentsecures and seals the components and layers beneath the diverter layer232 at the tissue site 108.

In one embodiment, the cover 244 may be an adhesive drape. The adhesionof the cover 244 may be due to the nature of the material with which thecover 244 is made, or may be due to an adhesive layer disposed on asurface of the cover 244. Any portion of the cover 244 may includeadhesive. For example, an entire tissue facing side of the cover 244 mayinclude adhesive. When provided with adhesive, the cover 244 may adhereto at least a portion of the tubing adapter 116, the tissue surroundingthe tissue site 108, or any layer or component of the reduced pressuredressing 104. In another embodiment, only the peripheral portions of thetissue facing side of the cover 244 may include adhesive. In thisparticular case, the adhesive-covered peripheral portions may be adaptedto adhere to any of the diverter layer 232, the seal layer 222, and thetissue surrounding the tissue site 108.

In still another embodiment, the cover 244 may be designed such that thecover 244 will not adhere to wet surfaces, but will adhere to drysurfaces. Thus, when applying the cover 244, the cover 244 will notstick to moistened gloves or hands, thereby permitting easier handlingof the cover 244 until the cover 244 is placed on a dry tissue site,such as a dry periwound area. The cover 244 may be any size, shape, orthickness. In one example, the cover 244 may be larger than any layer orcomponents of the reduced pressure dressing 104. In another example, thesize of the seal layer 222 may be larger than the size of the cover 244.

Reduced pressure may be applied to the plurality of layers of thereduced pressure dressing 104 via the aperture 260 in the cover 244. Inthe example of FIGS. 2 and 3, the aperture 260 is shown to be centrallylocated on the cover 244. However, the aperture 260 may be locatedanywhere on the cover 244, including a peripheral portion of the cover244 that is adjacent to an edge of cover 244. Although the aperture 260is shown to be circular, the aperture 260 may have any shape. In oneexample, the shape of the aperture is adapted to contour to one or moreportions of the tubing adapter 116.

The tubing adapter 116 provides an interface between conduit 112 and thereduced pressure dressing 104. In particular, the tubing adapter 116fluidly communicates with the conduit 112 such that the conduit 112transfers reduced pressure to the reduced pressure dressing 104 and thetissue site 108 via the tubing adapter 116.

Referring to FIGS. 1 and 2, the tubing adapter 116 may be a conventionalconnector pad that is adapted to abut or be partially disposed withinthe aperture 260. Alternatively, the tubing adapter 116 may have a lowprofile dome shape, or the tubing adapter 116 may be any other shape.The low profile of the tubing adapter 116 may help to keep the reducedpressure dressing 104 compact and convenient for use by a user. Thetubing adapter 116 includes a flange 266, which is disposed around theperiphery of the tubing adapter 116. In the embodiment illustrated inFIGS. 2 and 3, the tissue facing side of the cover 244 near the aperture260 may be adapted to adhere to the flange 266 such that the tubingadapter 116 is secured to at least one layer or component of the reducedpressure dressing 104.

Although not shown in FIGS. 2 and 3, in one embodiment the reducedpressure dressing 104 includes an odor filter. The odor filter retainsor prevents odor from exiting the reduced pressure dressing 104. Theodor filter may be a carbon odor filter, which may include charcoal. Inone example, the odor filter is a charcoal cloth. The odor filter may bepositioned anywhere in the reduced pressure dressing 104 such as, forexample, between the cover 244 and the liquid-air separator 240.

The reduced pressure dressing 104 may further include an indicator (notshown) to alert a user when the reduced pressure dressing 104 hasreached a full liquid storage capacity and needs to be removed from thetissue site 108. In one embodiment, the indicator may be a chemical orother substance that is capable of changing visual appearance or someother characteristic in the presence of moisture. For example, anindicator may be placed in one of the layers between the cover 244 andthe absorbent layer 228 such that the indicator undergoes a visiblecolor change when liquid has fully saturated the absorbent layer and ispulled through the absorbent layer into contact with the indicator. Inone embodiment, the indicator may be a part of the liquid-air separator240. The indicator may instead be a part of a separate indicator layerthat is positioned anywhere in the dressing to signal the presence ofmoisture in a particular area. The indicator may cooperate with anotherlayer of the dressing that is transparent to allow a user to view thelocation at which the indicator is positioned.

Although the cover 244, the liquid-air separator 240, the manifolds 224and 236, the diverter layer 232, the absorbent layer 228, the seal layer222, and the interface layer 220 have substantially square shapes inFIG. 3, each of these components, as well as other layers disclosedherein with respect to other embodiments, may have any shape as requiredto provide adequate reduced pressure therapy to the tissue site 108. Forexample, these components and layers may be polygonal, rectangular,circular, ovular, an irregular shape, a customized shape, or any othershape.

While the various layers of the reduced pressure dressing 104 have beendescribed as being “adjacent” to other layers, the term “adjacent” mayrefer to the layers being immediately adjacent, or alternatively thatthe layers may be positioned with other intervening layers in between.The term “layer” generally refers to portions or regions of the dressingthat have different material properties or functions than other portionsor regions of the dressing (i.e. other layers). The term “layer” is notmeant to be spatially limiting however. The properties and functionsassociated with a particular layer may be combined with the propertiesand functions of another layer such that a single layer having multipleand different properties and functions is created. More specifically,for example, two or more layers may be physically or chemically bondedor combined to create a single layer without affecting the originalmaterial properties or functions of the original components. Conversely,a particular layer of the dressings described herein may be broken intotwo or more layers that each have similar properties or functions.

Referring more specifically to FIG. 2, the specific arrangement of themultiple layers of the reduced pressure dressing 104 is described inmore detail. A tissue facing side 316 of the interface layer 220 isshown to be abutting the tissue site 108. In one example, the tissuefacing side 316 of the interface layer 220 has an uneven surface thatpromotes granulation of the tissue site 108 when reduced pressure isapplied through the interface layer 220. The uneven surface include afibrous surface that causes microstresses and strains on the tissue site108.

The seal layer 222 may be disposed anywhere between the cover 244 andinterface layer 220, including between the absorbent layer 228 andinterface layer 220. In the example of FIG. 2, the seal layer 222 isdisposed between the first manifold layer 224 and the interface layer220 such that a portion of a tissue facing side 327 of the seal layer222 abuts the interface layer 220. In particular, the tissue facing sideof an inner edge of the seal layer 222 that forms the aperture 231 abutsthe interface layer 220.

The seal layer 222 also includes overhanging portions 329, which extendpast the edges of the interface layer 220. The overhanging portions 329may be adapted to adhere or otherwise contact the tissue site 108 suchthat a seal is created at a portion of the tissue site 108. For example,the overhanging portion 329 may adhere or otherwise contact a periwoundarea surrounding a wound site such that a seal is created at the woundsite.

The first manifold layer 224 may also be disposed anywhere in thereduced pressure dressing 104. In one example, the first manifold layer224 is disposed between the interface layer 220 and the absorbent layer228. In the non-limiting example of FIG. 3, the first manifold layer 224is disposed between the seal layer 222 and the absorbent layer 228. Inparticular, a portion of a tissue facing side 336 of the first manifoldlayer 224 abuts the aperture 231 of the seal layer 222. In this example,a drape facing side 337 of the first manifold layer 224 abuts theabsorbent layer 228.

In the embodiment illustrated in FIG. 2, the absorbent layer 228 isshown to be disposed between the diverter layer 232 and the firstmanifold layer 224. A tissue facing side 342 of the absorbent layer 228abuts the first manifold layer 224. A drape facing side 343 of theabsorbent layer 228 abuts the diverter layer 232. In one example, thediverter layer 232 may be disposed between the absorbent layer 228 andthe cover 244. A tissue facing side 347 of the diverter layer 232 abutsthe absorbent layer 228. A drape facing side 348 of the diverter layer232 abuts the second manifold layer 236.

The second manifold layer 236 may be disposed between the absorbentlayer 228 and the cover 244, or between the diverter layer 232 and thecover 244. In FIG. 2, the second manifold layer 236 is disposed betweenthe liquid-air separator 240 and the diverter layer 232. A tissue facingside 352 of the second manifold layer 236 abuts the diverter layer 232.A drape facing side 353 of the second manifold layer 236 abuts theliquid-air separator 240.

The liquid-air separator 240 may be disposed between the absorbent layer228 and the cover 244, or between the second manifold layer 236 and thecover 244. In FIG. 2, a tissue facing side 356 of the liquid-airseparator 240 abuts the second manifold layer 236. A portion of a drapefacing side 357 of the liquid-air separator 240 abuts the tubing adapter116.

A tissue facing side 351 of the tubing adapter 116 abuts the liquid-airseparator 240. Also, a portion of the tubing adapter 116 is shown toprotrude from an aperture in the cover 244. The flange 266 of the tubingadapter 116 is sandwiched between the cover 244 and the liquid-airseparator 240 such that the cover 244 secures the tubing adapter 116 toat least one of the plurality of layers, such as the liquid-airseparator 240. As illustrated in FIG. 2, the liquid-air separator 240may be wider than the aperture 260 in the cover 244, and the secondmanifold layer 236 may be wider than the liquid-air separator 240.

The cover 244 may cover all or a part of the reduced pressure dressing104. For example, the ends of the cover 244 may terminate at a locationon the overhanging portions 329 of the seal layer 222. As indicated bythe broken lines 380, the cover 244 may also terminate at a location onthe tissue site 108.

Referring to FIG. 4, the diverter layer 232 includes a pattern of holes,or other apertures for applying the reduced pressure to portions of theabsorbent layer 228 (not shown). The holes have different diameters.More specifically, the diameter of holes 450 are larger than thediameter of holes 247. In operation, the diverter layer 232 channelsmore reduced pressure to the corners of a square absorbent layer 228 tofurther enhance the transmission capability of the absorbent layer 228because the corners are the last portion of the absorbent layer 228 tofill with liquid as liquid diffuses radially outward from the center ofthe absorbent layer 228.

Referring to FIGS. 5 and 6, a diverter layer 545 according to anillustrative embodiment may be made from any material that expands oncontact with a liquid. For example, the diverter layer 545 may be madefrom a hydrogel. The diverter layer 545 may also include a hydrocolloid,silicon, or silicone material. The diverter layer 545 includes holes547, or other apertures. The length of each of the arrows extending fromeach of the holes 547 represents the relative amount of flow or reducedpressure allowed through the holes. In FIG. 5, an equal amount of flowor reduced pressure is transferred through each of the holes 547.

In some reduced pressure applications, the tissue may produce moreexudate at an area away from the center of the dressing. In these cases,a greater amount of liquid may pass through a portion of the holes 547that are positioned over the main point of exudation. In the example ofFIG. 6, the main point of exudation occurs nearer to holes 648. Thus,the holes 648 are shown to be smaller, swelling, or substantially closedoff due to contact with liquid from the tissue site. The restriction ofthe holes 648 causes a preferential flow through the remaining holes547, thereby equalizing flow across an adjacent absorbent layer in thedressing. In particular, the holes 547 of diverter layer 545 as shown inFIG. 6 transmit a greater amount of reduced pressure than the holes 648.By equalizing flow and reduced pressure in such a manner, an absorbentlayer, such as absorbent layer 228 in FIGS. 2 and 3, may be more fullyutilized no matter the location of the main point of exudation at thetissue site, or the pattern with which the liquid is absorbed by theabsorbent layer.

Referring to FIGS. 7 and 8, a diverter layer 745 according to anillustrative embodiment includes a plurality of ridges 785 protrudingfrom a surface of the diverter layer 745 and extending radially outwardfrom the center to a periphery of the diverter layer 745 to form ordefine a plurality of channels 787 therebetween. The ridges 785 may becurved and may converge at a central portion of the diverter layer 745.The ridged face of the diverter 745 abuts an absorbent layer (not shown)so that the channels 787 are closed to form passages 887 and 888 (FIG.8) extending radially between the center portion and periphery of thediverter layer 745. In FIG. 8, each of the passages 887 are shown to beunobstructed, and therefore a substantially equal amount of reducedpressure freely flows through each one. However, in some reducedpressure applications, liquid from the tissue site 108 (not shown) fillsand obstructs the passages 888. This may occur, for example, when a mainpoint of exudation from the tissue site is located away from the centerof the dressing, including the diverter layer 745. Because a greateramount of liquid flows through the passages 888 than the passages 887,the passages 888 fill with the liquid and become obstructed by thesaturated portions of the absorbent layer 228 abutting the passages 888as indicated by shaded portions 889. Thus, as indicated by the arrows onthe diverter layer 745, a greater amount of reduced pressure is appliedthrough the passages 887 than the obstructed passages 888. The passages887 then become a preferential path for the reduced pressure and fluidflow until all of the absorbent layer 228 adjacent the diverter layer745 is saturated. By equalizing flow in such a manner, the absorbentlayer 228 is more fully utilized regardless of the location of the mainpoint of exudation on the tissue site, or the pattern with which theliquid is absorbed by the absorbent layer 228.

Referring to FIG. 9, a diverter layer 945 is shown according to anillustrative embodiment. The diverter layer 945 includes a pattern ofholes 947, or other apertures around a periphery of the diverter layer945. However, in contrast to the diverter layer 232 of FIGS. 2 and 3,the diverter layer 945 includes a portion 931 that does not includeholes 947. The portion 931 is capable of being aligned with a tubingadapter (similar to tubing adapter 116) that is positioned off-center.Because reduced pressure is applied to the dressing via the tubingadapter, the presence of holes directly underneath the tubing adapter,even with one or more intervening layers, may result in a larger thandesired portion of the reduced pressure being applied to the holesadjacent and underneath the tubing adapter Eliminating holes in theportion 931 of the diverter layer 945 that is adjacent and underneaththe tubing adapter applies the reduced pressure through all of theremaining holes 947 to more evenly distribute the reduced pressure tothe absorbent layer 228.

While the diverter layers of FIGS. 4-9 have been illustrated anddescribed as including substantially circular holes, the diverter layersmay instead include apertures of any shape or size, including forexample slots, slits, channels, perforations, or any other apertures.Alternatively, a diverter layer may be provided without apertures thatinstead is sized to be smaller in perimeter dimension and/or surfacearea than the absorbent layer. A diverter layer having a length or widthless than a length or width of the absorbent layer would ensure fluidflow travels around perimeter edges of the diverter layer, thus havingthe same effect as placement of apertures near an edge of a largerdiverter layer.

Referring to FIG. 10, a reduced pressure dressing 1000 is shownaccording to an illustrative embodiment. The reduced pressure dressing1000 is similar to the reduced pressure dressing 104 of FIGS. 2 and 3.The reduced pressure dressing 1000 is not shown with the tubing adapter116 or the cover 244 of FIGS. 2 and 3, but includes the absorbent layer228 and the diverter layer 232. The reduced pressure dressing 1000further includes a heat/moisture exchange (HME) foam 1015, which is anon-limiting example of the interface layer 220 in FIGS. 2 and 3. TheHME foam 1015 may be a hydrophilic foam that wicks liquid from thetissue site 108. The HME foam 1015 may also distribute reduced pressureto the tissue site. In one example, the tissue-facing side of the HMEfoam 1015 has an uneven surface such that granulation is promoted at thetissue site 108 when reduced pressure is applied through the HME foam1015. Each of the arrows in FIG. 10 represents the flow of either orboth of gas or liquid when reduced pressure is applied to the reducedpressure dressing 1000. The arrows illustrate how the diverter layer 232facilitates the distribution of gas and liquid throughout the reducedpressure dressing 1000 to more effectively utilize the absorbent layer228. For example, the arrows show that the presence of the diverterlayer 232 causes liquid to be drawn radially outward toward the edges ofthe absorbent layer 228 to more fully utilize the absorbent capacity ofthe absorbent layer 228.

The reduced pressure dressing 1000 also includes a second absorbentlayer 1040 disposed adjacent the diverter layer 232 on a side oppositethe first absorbent layer 228, and a second HME layer 1041 disposedadjacent the opposite side of the second absorbent layer 1040. Thesecond HME layer 1041 may be an open-celled and/or hydrophilic foam. Inone example, the HME layer 1041 is made of the same material as the HMEfoam 1015. Liquid from the tissue site 108 (not shown) is absorbed anddrawn into the HME foam 1015 and transferred to the absorbent layer 228.The liquid is absorbed by the absorbent layer 228, and is pulled throughthe holes 247 of the diverter layer 232, thereby spreading the liquidand leading to higher utilization of the absorbent layer 228. In thenon-limiting example in which a hydrogel diverter layer, such asdiverter layer 545 in FIG. 5, is used in lieu of the diverter layer 232,gel blocking can occur at the holes 247 so that liquid is forced to movearound in the absorbent layer 228 and is distributed. The secondabsorbent layer 1040 further absorbs any liquid flowing through thediverter layer 232 while the second HME layer 1041 manifolds a reducedpressure across the second absorbent layer 1040. In some cases, thesecond HME layer 1041 may be subjected to compression forces whenreduced pressure is applied through the reduced pressure dressing 1000.Despite such compression forces, the second HME layer 1041 may stillcontain open pressure channels that allow the second HME layer 1041 totransfer reduced pressure to other parts of the reduced pressuredressing 1000. A filter, such as liquid-air separator 240, may bepositioned above the HME layer 1041 to restrain or prevent the liquidfrom leaving the reduced pressure dressing 1000.

Referring to FIGS. 11 and 12, a drape 1125, or cover, is provided thatmay be used with a reduced pressure dressing such as, for example,reduced pressure dressing 104 of FIGS. 1-3. The drape 1125 includes anelastic portion 1110. The elastic portion 1110 is centrally located onthe drape 1125. The elastic portion 1110 may be made from any elasticmaterial. Also, although FIGS. 11 and 12 do not show an aperture on theelastic portion 1110, the elastic portion 1110 may include an aperture,such as the aperture 260 in FIG. 2. The aperture may be located anywhereon the elastic portion 1110. The elastic portion 1110 is bonded to aperipheral portion 1115 at a bonding area 1120. The bond at the bondingarea 1120 may be formed using any bonding technique. For example, theelastic portion 1110 may be glued or otherwise adhered to the peripheralportion 1115 at the bonding area 1120.

The peripheral portion 1115 may be made from any material, including anelastic or a non-elastic material. In one example, the peripheralportion 1115 includes an aperture. A tissue facing side 1122 of theperipheral portion 1115 may include an adhesive so that the drape 1125may be used to cover and secure one or more layers, such as the layersof reduced pressure dressing 104. In another embodiment, both theelastic portion 1110 and the peripheral portion 1115 may be made fromthe same material and be continuous with one another so that no bond isneeded between the elastic portion 1115 and the peripheral portion 1115at the bonding area 1120.

As illustrated in FIG. 12, the elastic portion 1110 may expand to aplurality of positions, from an unexpanded position shown by the solidline to an expanded position 1110 a shown by the broken line. As thereduced pressure dressing with which the drape 1125 is used fills withliquid, the elastic portion 1110 moves to the expanded position 1110 a.The ability of the drape 1125 to move to the expanded position 1110 aallows for additional room in the reduced pressure dressing for thestorage of liquid from the tissue site 108 (not shown).

As an alternative to a drape having an elastic portion, the drape 1125may instead be made from an inelastic material that is capable ofplastically deforming into an expanded position as fluid is collected ina dressing. The drape 1125 may instead include a combination of elasticand inelastic materials, and expansion may be based on both elastic andplastic deformation of the materials.

Referring to FIG. 13, a drape 1325, or cover, includes a pleated portion1310 that is centrally located on the drape 1310. The pleated portion1310 may be made from an elastic or a non-elastic material. The pleatedportion 1310 also includes one or more corrugations 1312, or ridges. Thecorrugations may be located on any or all sides of the pleated portion1310. Also, although FIG. 13 shows one corrugation on each side of thepleated portion 1310, each side of the pleated portion 1310 may includeany number of corrugations, which may form a bellows-like structure. Thepleated construction of the pleated portion 1310 allows the pleatedportion 1310 to expand as liquid is stored in an underlying reducedpressure dressing.

The drapes 1125 and 1325 of FIGS. 11-13 are capable of expanding toaccommodate fluid collection and storage in a reduced pressure dressing.It is also important to note that the drapes 1125 and 1325 are capableof maintaining reduced pressure in the dressing before, during, andafter expansion.

Referring to FIGS. 14 and 15, interface layers 1400 and 1500 areillustrated according to illustrative embodiments. The interface layers1400 and 1500 are tearable sheets foam material that include kiss-cutperforations 1405 and 1505 that allow for the easy tearing and sizing ofthe interface layers 1400 and 1500 for use in a dressing, such asreduced pressure dressing 104. In one example, when the interface layers1400 and 1500 are kiss-cut, the cutting die penetrates through most ofthe thickness of the foam material, but not fully. This provides aweakened path to tear along, while still allowing the foam to maintain ashape. In FIG. 14, the kiss-cut perforations 1405 are a series ofconcentric circles. A properly sized interface layer may be torn alongany one of the concentric circles. In FIG. 15, the kiss-cut perforation1505 is a continuous spiral-like perforation. The kiss-cut perforation1505 may be torn along this continuous perforation as needed to size theinterface layer prior to use with the dressing.

The kiss-cut perforations 1405 and 1505 provide a weakened path alongwhich the interface layer may be torn. When a portion of the interfacelayers 1400 and 1500 is used in a dressing, the interface layer maystill have some perforations remaining. However, despite having theseperforations, the interface layer is still able to maintain a desirableshape and effectively perform the functions of the interface layerdescribed herein.

Referring to FIG. 16, a graph 1600 that shows example characteristics ofa reduced pressure dressing is shown. The graph 1600 illustrates a dropin pressure measured as a function of time at an interface layer of areduced pressure dressing to which fluid is added at about 2 millilitersper hour. In particular, the graph 1600 shows a pressure measured at aninterface layer of a dressing that is about 8 cm² and includes an HMEfoam with a secondary Super Absorbent Fiber layer dressing mounted on alarge tube during the test. The reduced pressure applied to the dressingthroughout the test is a consistent 125 mmHg. As time passes and thedressing fills with fluid, the pressure eventually drops at theinterface layer as the dressing is no longer able to adequately manifoldreduced pressure. The graph 1600 represents characteristics of only oneparticular reduced pressure dressing, and other illustrative embodimentsof the dressing described herein may exhibit different characteristicsthan those shown in the graph 1600.

Referring to FIG. 17, a dressing 1700 according to an illustrativeembodiment includes an interface layer 1715. In contrast to theinterface layer 220 in FIG. 2, the interface layer 1715 has a largersize relative to the other layers in the dressing. The dressing 1700includes absorbent layer 228 above the tissue interface layer 1715, anddiverter layer 232 above the absorbent layer 228. In contrast to thereduced pressure dressing 104, the dressing 1700 includes anotherabsorbent layer 1740 above the diverter layer 232. The absorbent layer1740 is similar to the absorbent layer 228. The absorbent layer 1740 maybe added to increase the absorbency of the dressing 1700. The absorbentlayer 1740 may also be used to catch liquid that travels past or escapesfrom the absorbent layer 228.

The dressing 1700 includes second manifold layer 236 above the absorbentlayer 1740, and liquid-air separator 240 above the second manifold layer236. The dressing 1700 also includes a seal layer 1724 (similar to theseal layer 222 of FIG. 2) above the liquid-air separator 240. The seallayer 1724 has a circular aperture 1730, although the circular aperture1730 may be any shape. The dressing 1700 may also include a tubingadapter 1740 and cover 244. The tubing adapter 1740 may be a low-profiledome shape or any other shape.

In one embodiment, the components of the dressing 1700 that are adaptedto contact a tissue site are the tissue interface layer 1715, the seallayer 1724, and the cover 244. However, the components of the dressing1700 may be sized such that any of the components may come into contactwith the tissue site.

In another illustrative embodiment, a method is provided for collectingfluid in a dressing positioned at a tissue site. The method includesapplying a reduced pressure to the tissue site through the dressing,absorbing liquid from the tissue site, and storing the liquid in thedressing. The method further includes preventing the liquid from exitingthe dressing. In one embodiment, the step of absorbing liquid from thetissue site is accomplished with an absorbent layer similar to theabsorbent layers described herein. The method may further comprisediverting reduced pressure to a target region of the absorbent layer toincrease an absorption efficiency associated with the absorbent layer.Diversion of the reduced pressure to the target region may also increasean amount of time that the absorbent layer is able to distribute reducedpressure.

The illustrative embodiments of reduced pressure dressings describedherein may contain a diverter layer to ensure that even pressuredistribution is maintained as an absorbent layer absorbs fluid. Thediverter layer also promotes the efficient use of the absorbent materialin the dressing. The illustrative embodiments may also contain a poroushydrophobic filter that prevents the dressing from allowing liquid, suchas exudate, from entering a tubing and helping to ensure pressuredistribution. The construction of the dressing and the sequence oflayers in the illustrative embodiments help to ensure the optimalabsorbency of the dressing combined with the communication of reducedpressure to the tissue site.

Current wound dressings are designed to absorb liquid to maintain amoist wound environment while minimizing the risk of maceration, but areunsuited to adequately manifold reduced pressure. Current dressings thatare not currently used with reduced pressure will not normally transmitpressure to a tissue site. These current dressings are designed only toabsorb fluid and are routinely changed. The dressings described in theillustrative embodiments are adapted to provide therapy and moreabsorbent capacity both with and without reduced pressure, and may beapplied to a large variety of wounds, including low-severity wounds andlow-exudating wounds. The dressings described in the illustrativeembodiments will allow reduced pressure tissue therapy without impactingthe dressings' absorbency.

Without the diversion provided by components such as the diverter layer,liquid may be absorbed by the absorbent layer and concentrated into arestricted area around the point of exudation. This may lead to largeamounts of the absorbent layer being unused. For example, when a reducedpressure source of 125 mmHg is connected to a reduced pressure dressing,the absorbent material may release some of the absorbed liquid, whichwill bypass the rest of the absorbent area and be drawn directly intothe tube that connects the reduced pressure source to the dressing. Atthis point, the dressing may cease to absorb any more liquid, and as theliquid enters the tube, the dressing's ability to transmit reducedpressure to the tissue site is impaired. Furthermore, this may occurwhen only a fraction of the target fluid quantity has been absorbed.However, by using a diverter layer and other layers described herein,the efficiency of the absorbent layers may be increased so that thereduced pressure dressing is capable of absorbing more liquid andmanifolding reduced pressure for a longer period of time.

The components of the reduced pressure dressings described herein areillustrated in a non-limiting spatial configuration that may be altereddepending on the implementation. Although the figures show components ofthe reduced pressure dressings in a particular order, the components mayhave any order depending on the implementation. Similarly, the inclusionor exclusion of any particular component may vary depending on theparticular application.

Dressing with Integrated Pump

The reduced pressure dressings and components in FIGS. 1-17 have beendescribed as being adapted for connection to a reduced pressure sourceexternal to the dressing. However, the reduced pressure dressingsdescribed herein are also capable of incorporating an integrated pump,i.e. a pump positioned within or between layers of the dressing, todeliver reduced pressure through the layers of the dressing to thetissue site.

Referring to FIG. 18, a reduced pressure treatment system 1800 accordingto an illustrative embodiment includes a reduced pressure dressing 1804positioned at a tissue site 1808 of a patient. The reduced pressuredressing 1804 includes a reduced pressure pump 1810 that is integratedinto the reduced pressure dressing 1804. In addition to the reducedpressure pump 1810, other components may also be integrated into thedressing, including without limitation sensors, processing units,control units, alarm indicators, memory, databases, software.Additionally, the reduced pressure dressing 1804 may include interfaces(wireless or wired) that allow fluid communication between componentswithin the dressing 1804 and components that may be outside of thedressing 1804. In one non-limiting example, the interface may be a USBport. The external components may include without limitation controlunits, display units, battery chargers, and user interfaces that furtherfacilitate the application of reduced pressure treatment to the tissuesite 1808. Delivery of reduced pressure to the reduced pressure dressing1804 and tissue site 1808 by the reduced pressure pump 1810 encouragesnew tissue growth by maintaining drainage of exudate from the tissuesite, increasing blood flow to tissues surrounding the tissue site, andcreating microstrain at the tissue site.

Referring to FIGS. 19 and 20, the reduced pressure dressing 1804includes an interface layer 1920 adapted to be positioned at the tissuesite 1808, and a seal layer 1922 to seal the reduced pressure dressing1804 around the tissue site 1808. A first manifold layer 1924 ispositioned in fluid communication with the interface layer 1920 todistribute the reduced pressure to the interface layer 1920 and thetissue site 1808. An absorbent layer 1928 is positioned in fluidcommunication with the first manifold layer 1924 to absorb liquid fromat least one of the first manifold layer 1924, the interface layer 1920,and the tissue site 1808. A diverter layer 1932 positioned adjacent theabsorbent layer 1928. A second manifold layer 1936 is positioned influid communication with the diverter layer 1932, and a liquid-airseparator 1940 is positioned adjacent the second manifold layer 1936. Acover 1944, or drape, is positioned adjacent the second liquid-airseparator 1940. An indicator and odor filter may also be positionedwithin the reduced pressure dressing 1804.

The multiple layers of reduced pressure dressing 1804 are similar inshape, size, positioning, and function to the layers of any of the otherreduced pressure dressings described herein. In addition to the layersof dressing 1804 listed above, the reduced pressure dressing 1804includes a pump 1810 that may be integrated into the dressing betweenthe liquid-air separator 1940 and the cover 1944. The pump 1810 may be amicropump that is small and light enough such that the integratedreduced pressure dressing 1804 is able to be maintained on the tissuesite 1808. Furthermore, the size and weight of the pump 1810 should besuch that the integrated reduced pressure dressing 1804 does not pull orotherwise adversely affect the tissue site 1808. In one embodiment, thepump 1810 may be a disk pump having a piezoelectric actuator similar tothat described in International Patent Application No.PCT/GB2006/001487, published as WO 2006/111775, which is herebyincorporated by reference. In an alternative embodiment, the pump 1810may be a peristaltic pump that is used for pumping a variety of fluids.It should be understood that alternative pump technologies may beutilized and that rotary, linear, or other configurations of pumps maybe utilized.

The pump 1810 may be used to create enough reduced pressure to be“therapeutic” for wound therapy. In one embodiment, the pump 1810 hassufficient flow, vacuum, and operation life characteristics to enablecontinuous application of reduced pressure treatment. The flow may rangebetween about 5-1000 ml/min, the vacuum may range between about 50-200mmHg, and continuous operating life may last greater than 20 hours. Itshould be understood that alternative ranges may be utilized dependingon the configuration of the integrated reduced pressure dressing 1804,size of wound, type of wound, or otherwise. In one embodiment, multiplepumps may be positioned in a single dressing to deliver increased flowrates or vacuum levels as required. Alternatively, a selection of pumpshaving different operational capabilities and specifications may be kepton hand by a user or medical practitioner to allow optimization of apump and dressing combination for a particular tissue site.

The pump 1810 is disposed within the dressing to avoid conduits andexternal canisters for collection of wound exudate. The pump 1810 mayinclude a valve 1950 or outlet port to release air or exhaust out of thereduced pressure dressing 1804. If valve 1950 is used, the valve 1950may be in fluid communication with, or may be positioned within, anaperture 1960 of the cover 1944. Alternatively, the cover 1944 may besealed around an outlet port of the pump 1810 such that gas from thepump 1810 is able to exhaust directly through the aperture 1960. In theembodiment illustrated in FIGS. 18-20, the valve or outlet port of thepump 1810 is oriented in a direction away from the hydrophobic filter toavoid adding air to the wound dressing. The air exhausts through anaperture 1960 in the cover 1944, which may include a one-way valve.Alternatively, the air or other gas could be exhausted through agas-permeable portion of the cover 1944 as long as the ability of thecover 1944 to maintain reduced pressure is not affected.

When a piezoelectric-driven pump is used in a dressing, thepiezoelectric actuator associated with the pump may be driven atdifferent frequencies to act as a buzzer or vibrating alert system. Thealert system may be used to alert a user to an alarm condition such asthe presence of a leak in the dressing, a change in reduced pressure asmeasured by a sensor, an indication that the dressing has absorbed amaximum capacity of liquid as may be indicated by an indicator, or anindication that one or more layer are no longer manifolding reducedpressure efficiently.

Control electronics 2024 may be utilized to control operation of thepump 1810. The control electronics 2024 may be analog and/or digital andbe configured with a regulator (not shown) to regulate speed or dutycycle at which the pump 1810 operates. Furthermore, the controlelectronics 2024 may be configured with a controller (not shown) thatreceives sense signals from sensors or switches (not shown). The sensorsmay be disposed throughout the integrated reduced pressure dressing 1804to sense parameters, such as pressure, temperature, moisture, chemistry,odor, or any other parameter that may be utilized in managing andcontrolling the pump 1810. In one embodiment, the control electronics2024 include a computer processor. Alternatively, the controlelectronics 2024 may include a programmable gate array. Still yet, thecontrol electronics 2024 may be formed of analog electronic components.It should be understood that the control electronics 2024 may includeany form of digital and/or analog components to perform functionality asdescribed herein.

As understood in the art, there are four basic parameters that are ofconcern when performing reduced pressure wound treatment, including (i)low pressure, (ii) excessive leak, (iii) level of absorbent layer, and(iv) battery state. Accordingly, the control electronics 2024 mayinclude electronics that may be utilized to monitor each of the fourbasic parameters and generate an alarm signal (e.g., high-pitched beep,vibration, or light) using a speaker (not shown), vibrator (not shown),or illumination device (not shown), such as a light emitting diode(LED), to notify a medical professional, patient, or family member thata parameter is outside of a safe range. For example, if a pressure atthe wound site is below a therapeutic level, a continuous tone may begenerated. As another example, if the absorbent layer 1928 is saturated,then continuous beeps may be generated. Still yet, if the battery dropsbelow a certain voltage level, then a different frequency may begenerated and/or LED may be turned on. A variety of different alarmsignals may be established to notify a medical professional to take aparticular action.

A battery 2026 may be utilized to provide electric power to the pump1810 and control electronics 2024. The battery 2026 may have any sizeand shape configuration and be of any material, such as polymer, toaccommodate weight and size of the integrated reduced pressure dressing1804, as previously described. In one embodiment, the battery 2026 maybe rechargeable. In another embodiment, the battery 2026 may be disposedwithin or outside of the integrated reduced pressure dressing 1804 andbe positioned in such a manner as to allow for easy replacement orrecharging. In one embodiment, the battery 2026 may be configured with avoltage level sensor (not shown) that is monitored by the controlelectronics 2024 for determination of a low power level. In oneembodiment, the battery 2026 may be directly connected with the pump1810. Alternatively, the battery 2026 may be connected to the controlelectronics 2024 that use power from the battery 2026 to drive the pump1810. The control electronics 2024 may provide continuous power,modulated power, such as a pulsewidth modulated (PWM) signal, to drivethe pump 1810.

The seal layer 1922 may be adhered to or otherwise connected to thecover layer 1944 that is used to drape or otherwise cover the integratedreduced pressure dressing 1804. The seal layer 1922 may include anaggressive or medical grade adhesive material that is strong enough toform a vacuum seal with skin around a wound of a patient. The seal layer1922 may be a band that has an opening 2032 that is slightly larger thanthe geometric parameters as the hydrophobic filter 2020 or other layerso that the cover layer 2030 may contact skin around the wound site of apatient. The cover layer 2030 may be impermeable to fluids, such as airand liquids. In one embodiment, the cover layer 2030 includes a valve2034 to enable exhaust from the pump 1810 to be discharged from theintegrated reduced pressure dressing 1804. The valve 2034 may be aone-way valve to minimize fluids from entering into the integratedreduced pressure dressing 1804 via the cover layer 2030.

In another embodiment, the seal layer 1922 may be adhered to thediverter layer 1932 and the diverter layer 1932 adhered to the cover1944 to create an upper dressing portion and a lower dressing portion.The upper dressing portion may include the cover 1944, the pump 1810 andrelated components, the liquid-air separator 1940, the second manifoldlayer 1936, and the diverter layer 1932. The lower dressing portion mayinclude the absorbent layer 1928, the first manifold layer 1924, theseal layer 1922, and the interface layer 1920. In one embodiment, thereduced pressure dressing may be configured to allow replacement of thelower dressing portion once the dressing has absorbed a maximum capacityof fluid. The upper dressing portion may be reused after the lowerdressing portion is replaced. This allows multiple use of the pump 1810,while disposable portions of the dressing may be replaced. In anotherembodiment, the pump 1810, control electronics 2024, and battery 2026may be removed from the dressing for reuse and the remaining layers ofthe dressing replaced. In still another embodiment, the absorbent layer1928 only may be replaced. In yet another embodiment, the absorbentlayer 1928 and the interface layer 1920 only may be replaced.

A charcoal filter 2036 may be utilized in the integrated reducedpressure dressing 1804 to reduce odors created by the wound site anddispersed from the integrated reduced pressure dressing 1804. Thecharcoal filter 2036 may be disposed above a valve or other output ventfrom the pump 1810 to filter exhaust from the pump 1810 prior to beingreleased from the integrated reduced pressure dressing 1804. It shouldbe understood that the charcoal filter 2036 may be alternativelyconfigured and disposed above or below the pump 1810. Still yet, ratherthan using a charcoal filter, charcoal may be integrated into any or allof the different layers utilized in the integrated reduced pressuredressing 1804.

In another illustrative embodiment, a method for collecting liquid in adressing positioned at a tissue site includes generating a reducedpressure using a pump positioned within the dressing. A liquid isabsorbed from the tissue site and is stored in the dressing. The liquidis prevented from entering the pump. The method may further includemaintaining the reduced pressure within the dressing and exhausting gasfrom the pump outside the dressing.

It should be apparent from the foregoing that an invention havingsignificant advantages has been provided. While the invention is shownin only a few of its forms, it is not just limited but is susceptible tovarious changes and modifications without departing from the spiritthereof.

We claim:
 1. A dressing for treating a tissue site, comprising: anabsorbent layer adapted to be positioned at the tissue site to absorbliquid from the tissue site, the absorbent layer having a perimeterregion and a center region; a pump positioned within the dressing influid communication with the absorbent layer to provide reduced pressureto the absorbent layer; and a diverter layer comprising a substantiallygas-impermeable material adapted to be positioned in fluid communicationbetween the absorbent layer and the pump, wherein the diverter layerincludes a plurality of spaced apertures in fluid communication with theabsorbent layer.
 2. The dressing of claim 1, further comprising aliquid-air separator positioned between the absorbent layer and thepump, wherein the liquid-air separator substantially precludes liquidfrom entering the pump.
 3. The dressing of claim 1, wherein at least oneof the apertures is configured to become smaller on contact withmoisture.
 4. The dressing of claim 1, wherein the diverter layer isadapted to draw the liquid away from the center region of the absorbentlayer towards the perimeter region of the absorbent layer.
 5. Thedressing of claim 1, further comprising an interface layer adapted to bepositioned between the tissue site and the absorbent layer, wherein theinterface layer comprises foam.
 6. The dressing of claim 1, furthercomprising control electronics positioned within the dressing andoperatively connected to the pump.
 7. The dressing of claim 1, furthercomprising a seal layer configured to be positioned between the diverterlayer and tissue surrounding the tissue site.
 8. The dressing of claim1, wherein the diverter layer has a perimeter dimension that is smallerthan a perimeter dimension of the absorbent layer such that reducedpressure flow is directed around at least one perimeter edge of thediverter layer.
 9. The dressing of claim 1, wherein the diverter layerhas a surface area smaller than a surface area of the absorbent layersuch that reduced pressure flow is directed around at least oneperimeter edge of the diverter layer.
 10. The dressing of claim 1,wherein the diverter layer has a perimeter edge positioned substantiallywithin the perimeter region of the absorbent layer and away from thecenter region of the absorbent layer.
 11. The dressing of claim 1,wherein the diverter layer is positioned such that reduced pressure isapplied to the absorbent layer substantially through the perimeterregion of the absorbent layer and away from the center region of theabsorbent layer.
 12. The dressing of claim 1, wherein the pump is apiezoelectric-driven micropump.
 13. A system including the dressing ofclaim 1, further comprising: a cover adapted to be positioned over thedressing to provide a fluid seal relative to the tissue site; and anaperture in the cover to allow exhausting of gas from the pump.